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will a RC(nitro) engine benefit from a boost bottle?

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Old 03-24-2009, 11:21 PM
  #1
kawasaki_kid
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Default will a RC(nitro) engine benefit from a boost bottle?

A lot of what i know about tuning engines comes from a powersports back ground. i maintain my own snowmobile, dirtbike, ect. when i was younger i tuned the **** out of a 32cc scooter engine. one of the parts that made a significant differance was a boost bottle. A boost bottle is NOT a nitrous type system. If you dont know what a boost bottle is, i have included an explination.

i was wondering if the same principles will work on a 3.0 HPI? does anyone manufacture this type of product?

How does a boost bottle work?

It's function is to absorb & release pressure pulses within the intake vein, assisting engine breathing. Now an explanation of exactly what goes on involves a lot of physics and a good understanding of fluid dynamics & pressure zones, but can be explained rather easily. During the intake stroke, air is sucked through the intake manifold and into the port at a considerable velocity. Because of this velocity, the air is said to have relative inertia. Now, when the intake valve closes, the kinetically charged air suddenly has nowhere to go, creating a high-pressure area. Naturally, the air wants to release its pressure in the easiest way possible, so it tries to shoot back out the way it came, creating a pressure wave in the opposite direction we want it. Then no sooner dose the wave begin to travel, the intake valve suddenly opens again leaving the motor to try and pull the pressure wave back in again. This dramatically effects low RPM, wastes energy and kills low-end performance. Now the same engine, but with a BOOST BOTTLE. Air goes whistling down the manifold until the intake valve closes. The air, still all charged up with energy tries to escape back up the manifold but is met with a small port that has a residual vacuum. This vacuum being caused by the previous suction of the intake stroke, sucks most of the pulse inside the Boost Bottle, storing much of the pulse’s energy. The intake valve then suddenly opens, creating a low-pressure area outside of the Boost Bottle. The gasses then shoot out of the Boost Bottle, directly into the intake system as a pressure pulse, instead of having to be pulled in by the piston. More air is then also pulled in from the manifold to completely fill the cylinder… Thus giving you an additional boost of power.

Boost bottle kits are not Nitrous Oxide (NOS)
Boost bottles work off the combustion of your engine and do not require any fuel additives or maintenance. A boost bottle will last the life of your engine and does not pose any danger to your engine mechanically.

i was wondering if the same principles will work on a 3.0 HPI?
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Old 03-25-2009, 10:02 AM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

From what I've read, boost bottles do work, but those available for RC engines are generally improperly designed and therefore show little, if any gains.

They can also cause problems if installed incorrectly (load up with fuel, inconsistent idle, etc.)

Seems to me all they do could be obtained by a longer intake, but I've never seen an extension to go between carb and engine available for that purpose.
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Old 03-25-2009, 08:09 PM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

I don't know if I'm convinced... until someone shows me a dyno sheet of a motor before and after a boost bottle I'm gonna call it snake oil. The timing of the motor would have to be absolutly perfect in order for the air to move in and out at the right time. They might work but no one has any real proof. I'm guessing it's a crap shoot. Some motors might have the right timing profile to take advantage of one and others migh run worse on it. I could be wrong but keep in mind your drilling a hole in the crankcase. If you don't like it... your stuck with that hole unless you swap cases.
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Old 03-25-2009, 10:35 PM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

Ofna has the Hyper .21 8 port race w/boost....check it out...is that what your talking about?
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Old 03-26-2009, 06:30 AM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

I hadn't noticed boost bottles were ported into the crankcase, but I guess that makes sense, as there is no intake manifold to speak of. In larger gasoline engines, it is usually "T'd" into the intake manifold.

There are some guidelines on connection (hose and fitting) diameter compared to manifold diameter and bottle size compared to engine displacement. It appears most boost bottles available for nitro (and for that matter, those 1/5 gassers, such as the 5B) are incorrectly sized to work.

Some motorcycle manufacturers have used boost bottles to significant advantage on their products.
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Old 03-26-2009, 07:22 PM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

Interesting theories about this. I imagine it might work in a very narrow rpm range.

Someone should make a dyno run and compare with and without boost bottle.
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Old 03-26-2009, 11:34 PM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

Sorry but it won't work. On our size engines there's only about an inch or so of length from the carb mouth to the crankshaft port so inertial mass is tiny to start with. Then with the crankshaft porting remaining open until around 45 degrees after the piston starts down the small air column begins to slow down anyway before the port finishes closing. The better way to do things is to open up the volume below the spray bar which reduces the air speed below the venturi. Reducing air speed increases pressure above the inlet port and this pressure helps the mixture go through the port faster. Ideally the area below the venturi should be flared out to match the size and shape of the casting where the carb plugs in to give a kind of plenum chamber and reduce any turbulence as much as possible.
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Old 03-27-2009, 06:25 AM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

I really like all the Australians that post on the various RC sites. They really get into the science of the hobby! Great contributors! Keep up the good work!
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Old 03-27-2009, 08:47 PM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

How long do yall think it will be before a manufacture comes up with an engine specifically designed to use one on it?
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Old 03-28-2009, 08:22 AM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

Never. If it could be done it would already have been done because there are some very smart people building extreme high performance engines that only have one speed and that's flat out. Believe it or not, the best engines produce as much power for their size as a supercharged nitro burning drag race engine and that's with only methanol as the fuel.
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Old 03-28-2009, 11:52 PM
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Default RE: will a RC(nitro) engine benefit from a boost bottle?

Good Point.... My guess is that with those superchargers and other things would just shoot the fuel right over the piston since it is only a 2-cycle engine?
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